Rockwall: The Town Named for a Mystery in the Ground

When settlers started digging wells near here in the eighteen fifties, they kept hitting something strange: a continuous buried wall of rock running in straight lines beneath the soil. Early residents were convinced they had found the ruins of an ancient civilization, and the county they formed in eighteen seventy-three took its name from the formation. The mystery lingered for over a century.

Geologists eventually concluded it is a natural phenomenon, a series of sandstone dikes formed when sediment filled fractures in the rock, but debate never fully settled. Rockwall County is the smallest county by area in Texas, a distinction it carries despite now being a fast-growing suburb of Dallas. The buried wall that gave it a name is still out there, under the subdivisions.